[2021] Is it worth it to spend 8.3M credits for a supercontainer?

Generally I would say "yes, a SC is worth 8.3 million credits".
Even if you get x100 det flags, those x100 flags are worth something like 11 million credits (math off the top of my head...)
The FXP, Dubs, Ships, and Premium Signals you can get are well worth it.
If you get x50 camos that are +100% xp, it might not be, but generally I'd say it's worth it :)